kernel/audit_watch.c

   1 /* audit_watch.c -- watching inodes
   2  *
   3  * Copyright 2003-2009 Red Hat, Inc.
   4  * Copyright 2005 Hewlett-Packard Development Company, L.P.
   5  * Copyright 2005 IBM Corporation
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/audit.h>
  24 #include <linux/kthread.h>
  25 #include <linux/mutex.h>
  26 #include <linux/fs.h>
  27 #include <linux/fsnotify_backend.h>
  28 #include <linux/namei.h>
  29 #include <linux/netlink.h>
  30 #include <linux/sched.h>
  31 #include <linux/slab.h>
  32 #include <linux/security.h>
  33 #include "audit.h"
  34
  35 /*
  36  * Reference counting:
  37  *
  38  * audit_parent: lifetime is from audit_init_parent() to receipt of an FS_IGNORED
  39  *      event.  Each audit_watch holds a reference to its associated parent.
  40  *
  41  * audit_watch: if added to lists, lifetime is from audit_init_watch() to
  42  *      audit_remove_watch().  Additionally, an audit_watch may exist
  43  *      temporarily to assist in searching existing filter data.  Each
  44  *      audit_krule holds a reference to its associated watch.
  45  */
  46
  47 struct audit_watch {
  48         atomic_t                count;  /* reference count */
  49         dev_t                   dev;    /* associated superblock device */
  50         char                    *path;  /* insertion path */
  51         unsigned long           ino;    /* associated inode number */
  52         struct audit_parent     *parent; /* associated parent */
  53         struct list_head        wlist;  /* entry in parent->watches list */
  54         struct list_head        rules;  /* anchor for krule->rlist */
  55 };
  56
  57 struct audit_parent {
  58         struct list_head        watches; /* anchor for audit_watch->wlist */
  59         struct fsnotify_mark mark; /* fsnotify mark on the inode */
  60 };
  61
  62 /* fsnotify handle. */
  63 struct fsnotify_group *audit_watch_group;
  64
  65 /* fsnotify events we care about. */
  66 #define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
  67                         FS_MOVE_SELF | FS_EVENT_ON_CHILD)
  68
  69 static void audit_free_parent(struct audit_parent *parent)
  70 {
  71         WARN_ON(!list_empty(&parent->watches));
  72         kfree(parent);
  73 }
  74
  75 static void audit_watch_free_mark(struct fsnotify_mark *entry)
  76 {
  77         struct audit_parent *parent;
  78
  79         parent = container_of(entry, struct audit_parent, mark);
  80         audit_free_parent(parent);
  81 }
  82
  83 static void audit_get_parent(struct audit_parent *parent)
  84 {
  85         if (likely(parent))
  86                 fsnotify_get_mark(&parent->mark);
  87 }
  88
  89 static void audit_put_parent(struct audit_parent *parent)
  90 {
  91         if (likely(parent))
  92                 fsnotify_put_mark(&parent->mark);
  93 }
  94
  95 /*
  96  * Find and return the audit_parent on the given inode.  If found a reference
  97  * is taken on this parent.
  98  */
  99 static inline struct audit_parent *audit_find_parent(struct inode *inode)
 100 {
 101         struct audit_parent *parent = NULL;
 102         struct fsnotify_mark *entry;
 103
 104         entry = fsnotify_find_inode_mark(audit_watch_group, inode);
 105         if (entry)
 106                 parent = container_of(entry, struct audit_parent, mark);
 107
 108         return parent;
 109 }
 110
 111 void audit_get_watch(struct audit_watch *watch)
 112 {
 113         atomic_inc(&watch->count);
 114 }
 115
 116 void audit_put_watch(struct audit_watch *watch)
 117 {
 118         if (atomic_dec_and_test(&watch->count)) {
 119                 WARN_ON(watch->parent);
 120                 WARN_ON(!list_empty(&watch->rules));
 121                 kfree(watch->path);
 122                 kfree(watch);
 123         }
 124 }
 125
 126 void audit_remove_watch(struct audit_watch *watch)
 127 {
 128         list_del(&watch->wlist);
 129         audit_put_parent(watch->parent);
 130         watch->parent = NULL;
 131         audit_put_watch(watch); /* match initial get */
 132 }
 133
 134 char *audit_watch_path(struct audit_watch *watch)
 135 {
 136         return watch->path;
 137 }
 138
 139 int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
 140 {
 141         return (watch->ino != (unsigned long)-1) &&
 142                 (watch->ino == ino) &&
 143                 (watch->dev == dev);
 144 }
 145
 146 /* Initialize a parent watch entry. */
 147 static struct audit_parent *audit_init_parent(struct nameidata *ndp)
 148 {
 149         struct inode *inode = ndp->path.dentry->d_inode;
 150         struct audit_parent *parent;
 151         int ret;
 152
 153         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
 154         if (unlikely(!parent))
 155                 return ERR_PTR(-ENOMEM);
 156
 157         INIT_LIST_HEAD(&parent->watches);
 158
 159         fsnotify_init_mark(&parent->mark, audit_watch_free_mark);
 160         parent->mark.mask = AUDIT_FS_WATCH;
 161         ret = fsnotify_add_mark(&parent->mark, audit_watch_group, inode, NULL, 0);
 162         if (ret < 0) {
 163                 audit_free_parent(parent);
 164                 return ERR_PTR(ret);
 165         }
 166
 167         fsnotify_recalc_group_mask(audit_watch_group);
 168
 169         return parent;
 170 }
 171
 172 /* Initialize a watch entry. */
 173 static struct audit_watch *audit_init_watch(char *path)
 174 {
 175         struct audit_watch *watch;
 176
 177         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 178         if (unlikely(!watch))
 179                 return ERR_PTR(-ENOMEM);
 180
 181         INIT_LIST_HEAD(&watch->rules);
 182         atomic_set(&watch->count, 1);
 183         watch->path = path;
 184         watch->dev = (dev_t)-1;
 185         watch->ino = (unsigned long)-1;
 186
 187         return watch;
 188 }
 189
 190 /* Translate a watch string to kernel respresentation. */
 191 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
 192 {
 193         struct audit_watch *watch;
 194
 195         if (!audit_watch_group)
 196                 return -EOPNOTSUPP;
 197
 198         if (path[0] != '/' || path[len-1] == '/' ||
 199             krule->listnr != AUDIT_FILTER_EXIT ||
 200             op != Audit_equal ||
 201             krule->inode_f || krule->watch || krule->tree)
 202                 return -EINVAL;
 203
 204         watch = audit_init_watch(path);
 205         if (IS_ERR(watch))
 206                 return PTR_ERR(watch);
 207
 208         audit_get_watch(watch);
 209         krule->watch = watch;
 210
 211         return 0;
 212 }
 213
 214 /* Duplicate the given audit watch.  The new watch's rules list is initialized
 215  * to an empty list and wlist is undefined. */
 216 static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
 217 {
 218         char *path;
 219         struct audit_watch *new;
 220
 221         path = kstrdup(old->path, GFP_KERNEL);
 222         if (unlikely(!path))
 223                 return ERR_PTR(-ENOMEM);
 224
 225         new = audit_init_watch(path);
 226         if (IS_ERR(new)) {
 227                 kfree(path);
 228                 goto out;
 229         }
 230
 231         new->dev = old->dev;
 232         new->ino = old->ino;
 233         audit_get_parent(old->parent);
 234         new->parent = old->parent;
 235
 236 out:
 237         return new;
 238 }
 239
 240 static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
 241 {
 242         if (audit_enabled) {
 243                 struct audit_buffer *ab;
 244                 ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
 245                 audit_log_format(ab, "auid=%u ses=%u op=",
 246                                  audit_get_loginuid(current),
 247                                  audit_get_sessionid(current));
 248                 audit_log_string(ab, op);
 249                 audit_log_format(ab, " path=");
 250                 audit_log_untrustedstring(ab, w->path);
 251                 audit_log_key(ab, r->filterkey);
 252                 audit_log_format(ab, " list=%d res=1", r->listnr);
 253                 audit_log_end(ab);
 254         }
 255 }
 256
 257 /* Update inode info in audit rules based on filesystem event. */
 258 static void audit_update_watch(struct audit_parent *parent,
 259                                const char *dname, dev_t dev,
 260                                unsigned long ino, unsigned invalidating)
 261 {
 262         struct audit_watch *owatch, *nwatch, *nextw;
 263         struct audit_krule *r, *nextr;
 264         struct audit_entry *oentry, *nentry;
 265
 266         mutex_lock(&audit_filter_mutex);
 267         /* Run all of the watches on this parent looking for the one that
 268          * matches the given dname */
 269         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
 270                 if (audit_compare_dname_path(dname, owatch->path, NULL))
 271                         continue;
 272
 273                 /* If the update involves invalidating rules, do the inode-based
 274                  * filtering now, so we don't omit records. */
 275                 if (invalidating && !audit_dummy_context())
 276                         audit_filter_inodes(current, current->audit_context);
 277
 278                 /* updating ino will likely change which audit_hash_list we
 279                  * are on so we need a new watch for the new list */
 280                 nwatch = audit_dupe_watch(owatch);
 281                 if (IS_ERR(nwatch)) {
 282                         mutex_unlock(&audit_filter_mutex);
 283                         audit_panic("error updating watch, skipping");
 284                         return;
 285                 }
 286                 nwatch->dev = dev;
 287                 nwatch->ino = ino;
 288
 289                 list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
 290
 291                         oentry = container_of(r, struct audit_entry, rule);
 292                         list_del(&oentry->rule.rlist);
 293                         list_del_rcu(&oentry->list);
 294
 295                         nentry = audit_dupe_rule(&oentry->rule);
 296                         if (IS_ERR(nentry)) {
 297                                 list_del(&oentry->rule.list);
 298                                 audit_panic("error updating watch, removing");
 299                         } else {
 300                                 int h = audit_hash_ino((u32)ino);
 301
 302                                 /*
 303                                  * nentry->rule.watch == oentry->rule.watch so
 304                                  * we must drop that reference and set it to our
 305                                  * new watch.
 306                                  */
 307                                 audit_put_watch(nentry->rule.watch);
 308                                 audit_get_watch(nwatch);
 309                                 nentry->rule.watch = nwatch;
 310                                 list_add(&nentry->rule.rlist, &nwatch->rules);
 311                                 list_add_rcu(&nentry->list, &audit_inode_hash[h]);
 312                                 list_replace(&oentry->rule.list,
 313                                              &nentry->rule.list);
 314                         }
 315
 316                         audit_watch_log_rule_change(r, owatch, "updated rules");
 317
 318                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 319                 }
 320
 321                 audit_remove_watch(owatch);
 322                 goto add_watch_to_parent; /* event applies to a single watch */
 323         }
 324         mutex_unlock(&audit_filter_mutex);
 325         return;
 326
 327 add_watch_to_parent:
 328         list_add(&nwatch->wlist, &parent->watches);
 329         mutex_unlock(&audit_filter_mutex);
 330         return;
 331 }
 332
 333 /* Remove all watches & rules associated with a parent that is going away. */
 334 static void audit_remove_parent_watches(struct audit_parent *parent)
 335 {
 336         struct audit_watch *w, *nextw;
 337         struct audit_krule *r, *nextr;
 338         struct audit_entry *e;
 339
 340         mutex_lock(&audit_filter_mutex);
 341         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 342                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 343                         e = container_of(r, struct audit_entry, rule);
 344                         audit_watch_log_rule_change(r, w, "remove rule");
 345                         list_del(&r->rlist);
 346                         list_del(&r->list);
 347                         list_del_rcu(&e->list);
 348                         call_rcu(&e->rcu, audit_free_rule_rcu);
 349                 }
 350                 audit_remove_watch(w);
 351         }
 352         mutex_unlock(&audit_filter_mutex);
 353
 354         fsnotify_destroy_mark(&parent->mark);
 355
 356         fsnotify_recalc_group_mask(audit_watch_group);
 357
 358 }
 359
 360 /* Get path information necessary for adding watches. */
 361 static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
 362 {
 363         struct nameidata *ndparent, *ndwatch;
 364         int err;
 365
 366         ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
 367         if (unlikely(!ndparent))
 368                 return -ENOMEM;
 369
 370         ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
 371         if (unlikely(!ndwatch)) {
 372                 kfree(ndparent);
 373                 return -ENOMEM;
 374         }
 375
 376         err = path_lookup(path, LOOKUP_PARENT, ndparent);
 377         if (err) {
 378                 kfree(ndparent);
 379                 kfree(ndwatch);
 380                 return err;
 381         }
 382
 383         err = path_lookup(path, 0, ndwatch);
 384         if (err) {
 385                 kfree(ndwatch);
 386                 ndwatch = NULL;
 387         }
 388
 389         *ndp = ndparent;
 390         *ndw = ndwatch;
 391
 392         return 0;
 393 }
 394
 395 /* Release resources used for watch path information. */
 396 static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
 397 {
 398         if (ndp) {
 399                 path_put(&ndp->path);
 400                 kfree(ndp);
 401         }
 402         if (ndw) {
 403                 path_put(&ndw->path);
 404                 kfree(ndw);
 405         }
 406 }
 407
 408 /* Associate the given rule with an existing parent.
 409  * Caller must hold audit_filter_mutex. */
 410 static void audit_add_to_parent(struct audit_krule *krule,
 411                                 struct audit_parent *parent)
 412 {
 413         struct audit_watch *w, *watch = krule->watch;
 414         int watch_found = 0;
 415
 416         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 417
 418         list_for_each_entry(w, &parent->watches, wlist) {
 419                 if (strcmp(watch->path, w->path))
 420                         continue;
 421
 422                 watch_found = 1;
 423
 424                 /* put krule's and initial refs to temporary watch */
 425                 audit_put_watch(watch);
 426                 audit_put_watch(watch);
 427
 428                 audit_get_watch(w);
 429                 krule->watch = watch = w;
 430                 break;
 431         }
 432
 433         if (!watch_found) {
 434                 audit_get_parent(parent);
 435                 watch->parent = parent;
 436
 437                 list_add(&watch->wlist, &parent->watches);
 438         }
 439         list_add(&krule->rlist, &watch->rules);
 440 }
 441
 442 /* Find a matching watch entry, or add this one.
 443  * Caller must hold audit_filter_mutex. */
 444 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 445 {
 446         struct audit_watch *watch = krule->watch;
 447         struct audit_parent *parent;
 448         struct nameidata *ndp = NULL, *ndw = NULL;
 449         int h, ret = 0;
 450
 451         mutex_unlock(&audit_filter_mutex);
 452
 453         /* Avoid calling path_lookup under audit_filter_mutex. */
 454         ret = audit_get_nd(watch->path, &ndp, &ndw);
 455         if (ret) {
 456                 /* caller expects mutex locked */
 457                 mutex_lock(&audit_filter_mutex);
 458                 goto error;
 459         }
 460
 461         mutex_lock(&audit_filter_mutex);
 462
 463         /* update watch filter fields */
 464         if (ndw) {
 465                 watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
 466                 watch->ino = ndw->path.dentry->d_inode->i_ino;
 467         }
 468
 469         /* either find an old parent or attach a new one */
 470         parent = audit_find_parent(ndp->path.dentry->d_inode);
 471         if (!parent) {
 472                 parent = audit_init_parent(ndp);
 473                 if (IS_ERR(parent)) {
 474                         ret = PTR_ERR(parent);
 475                         goto error;
 476                 }
 477         }
 478
 479         audit_add_to_parent(krule, parent);
 480
 481         /* match get in audit_find_parent or audit_init_parent */
 482         audit_put_parent(parent);
 483
 484         h = audit_hash_ino((u32)watch->ino);
 485         *list = &audit_inode_hash[h];
 486 error:
 487         audit_put_nd(ndp, ndw);         /* NULL args OK */
 488         return ret;
 489
 490 }
 491
 492 void audit_remove_watch_rule(struct audit_krule *krule)
 493 {
 494         struct audit_watch *watch = krule->watch;
 495         struct audit_parent *parent = watch->parent;
 496
 497         list_del(&krule->rlist);
 498
 499         if (list_empty(&watch->rules)) {
 500                 audit_remove_watch(watch);
 501
 502                 if (list_empty(&parent->watches)) {
 503                         audit_get_parent(parent);
 504                         fsnotify_destroy_mark(&parent->mark);
 505                         audit_put_parent(parent);
 506                 }
 507         }
 508
 509         fsnotify_recalc_group_mask(audit_watch_group);
 510
 511 }
 512
 513 static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode,
 514                                           struct vfsmount *mnt, struct fsnotify_mark *mark,
 515                                           __u32 mask, void *data, int data_type)
 516 {
 517        return true;
 518 }
 519
 520 /* Update watch data in audit rules based on fsnotify events. */
 521 static int audit_watch_handle_event(struct fsnotify_group *group,
 522                                     struct fsnotify_mark *mark,
 523                                     struct fsnotify_event *event)
 524 {
 525         struct inode *inode;
 526         __u32 mask = event->mask;
 527         const char *dname = event->file_name;
 528         struct audit_parent *parent;
 529
 530         parent = container_of(mark, struct audit_parent, mark);
 531
 532         BUG_ON(group != audit_watch_group);
 533
 534         switch (event->data_type) {
 535         case (FSNOTIFY_EVENT_FILE):
 536                 inode = event->file->f_path.dentry->d_inode;
 537                 break;
 538         case (FSNOTIFY_EVENT_INODE):
 539                 inode = event->inode;
 540                 break;
 541         default:
 542                 BUG();
 543                 inode = NULL;
 544                 break;
 545         };
 546
 547         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 548                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 549         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 550                 audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
 551         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 552                 audit_remove_parent_watches(parent);
 553
 554         return 0;
 555 }
 556
 557 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 558         .should_send_event =    audit_watch_should_send_event,
 559         .handle_event =         audit_watch_handle_event,
 560         .free_group_priv =      NULL,
 561         .freeing_mark =         NULL,
 562         .free_event_priv =      NULL,
 563 };
 564
 565 static int __init audit_watch_init(void)
 566 {
 567         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
 568         if (IS_ERR(audit_watch_group)) {
 569                 audit_watch_group = NULL;
 570                 audit_panic("cannot create audit fsnotify group");
 571         }
 572         return 0;
 573 }
 574 device_initcall(audit_watch_init);